Let-off mechanism for looms



Au 22, 1939. o. MOBERG LET-Q?!" MECHANISM FOR LOOMS 2 Sheets-Sheet 1INVENTOR Filed July 28, 1938 ATTORNEY.

Aug. 22, 1939. b, Q' R 2,170,762

LET-OFF MECHANISM FOR LOOMS Filed July 28, 1938 2 Sheets-Sheet 2 CZINVENTOR ATTORNEY.

Patented Aug. 22, 1939 Ivar 0. Moberg, Lowell, Mass.,

assignor to Nashua Manufacturing Company, Nashua,

N. H., a corporation Application July 28,

6 Claims.

This invention relates to looms and is more especially concerned withthe mechanisms used in connection with weaving from beamed warp to letoff the yarn at the rate required for the weaving operations.

It is the chief object of the invention to improve these so-calledlet-off mechanisms with a view to making them more completely automaticin operation, while at the same time providing a simple, reliable andsturdy construction capable of giving long service with a minimum ofattention.

The nature of the invention will be readily understood from thefollowing description when read in connection with the accompanyingdrawings, and the novel features will be particularly pointed out in theappended claims.

In the drawings:

Figure 1 is a side elevation, somewhat diagrammatic in character,showing those parts of a loom with which the invention is moreespecially concerned and illustrating a. let-off mechanism embodying theinvention;

Fig. 2 is a sectional view approximately on the,

line 22, Fig. 1;

Fig. 3 is a sectional view approximately on the line 33, Fig. 2; and

Fig. 4 is a View similar to Fig. 3 illustrating the parts in a differentposition.

Referring first to Fig. 1, the loom structure there shown comprises alay 2 mounted to swing in a rock shaft 3 and driven by the usual pitmanor connecting rod from the lay shaft 4. The warp is supported on a beam5 which is mounted in the usual manner, the warp yarns being led overthe whip roll 6 and running thence through the shedding mechanism to thefell of the cloth W being woven. This roll is supported in the usualmanner on arms or fingers secured on the whip roll shaft 1, one of thesearms or fingers being indicated at 8. In order to apply the desireddegree of tension to the roll, another arm It! extends downwardly fromthe shaft 1 and is connected by a head I l toone end of a U-shapedtension link I 2, the opposite end of which extends through an eye inthe upper end of a let-off lever l3. A bearing I4 fixed on the framesupports the link for sliding movement therethrough and a tensioningspring I 5 which encircles the link bears at one end against the bearingand at the opposite end against the collar l6 secured on one leg of saidlink A buffer spring I! is similarly associated with the other leg ofthe link and is interposed between the eye'of the lever l3 and anothercollar l8 with which the link is equipped.

of New Hampshire 1938, Serial No. 221,763

The let-ofi mechanism is driven by a slide or driver 20 formed on thefree end of a link 2|, the opposite end of which is pivoted to an arm 22secured fast on the rock shaft 3 for the lay. It slides on a rod 23which is pivoted to a rocker 24 carrying the pawl 25 and mounted tooscillate around the axis of the shaft 26. A sleeve 27 also mounted onthe shaft carries a worm 28 meshing with a worm gear 30. On the sameshaft with this gear is another gear 3| which drives the beam gear 32.

The construction above described is the well known Bartlett let-offmotion. In addition to the parts mentioned, it includes a collar orblock 33 adjustably mounted on the pawl operating rod 23 and a secondcollar or block 34 is similarly secured to said rod and pivoted to thelower end of the left-off lever l3.

When the loom is running the spring l5 operates through the whip roll 6to maintain a strong tension on the warp threads or yarns y, thistension being so balanced against the frictional drag applied to thebeam as to hold it approximately in the position shown in Fig. 1. Duringeach beat-up motion of the lay the driver 20 is moved to the right untilit strikes the block 33, whereupon it carries the block with it and thusproduces an operating movement of the pawl 25, the ratchet wheel 29, andthrough the reduction gearing between it and the beam '52, moving thebeam slightly in a clockwise direction so as to let off a certain amountof warp. The extent of this let-off movement, however, is controlled bythe position of the whip roll 6, since this position determines thereturn or idle movement of the pawl. In other words, the spring I!operates through the let-off lever [3 to return the rod 23 andconsequently the block 33, after each let-01f movement, to a positionwhich depends upon the position of the Whip roll 5. If the let-offmechanism does not feed yarn at the rate required by the weavinginstrumentalities, the whip roll-6 will be depressed, thus operatingthrough its connections with the rod 23 to move this rod toward theleft. Consequently, upon the next beat-up of the lay the driver 20 willstrike the block 33 at an earlier point in the stroke of the driver thanpreviously and will give the beam an increased let-off movement. Thusthe whip roll position governs the relationship between the idle portionof the movement, of the driver 20 and the useful fraction of thatmovement in each beatup of the lay.

It will be evident that as the diameter of the yarn body on the beam 5is reduced during the continued operation of the loom, a greaterrotative movement must be imparted to it in order to deliver the samelength of warp. In the mechanism so far described this demand for anincreased rate of warp let-off results in depressing the whip rollfurther and thereby reducing the lost motion of the pawl drivingmechanism so that the pawl will take more teeth on the ratchet wheel ateach let-01f. However, the constant lowering of the whip rollnecessarily compresses the tensioning spring or springs to a greaterdegree and thereby undesirably increases the tension on the warp. Sincethis increased tension tends to reduce the width of the goods beingwoven and to increase the number of picks per inch, it becomes necessaryto loosen up the springs l5 from time to time. A further disadvantage ofthis arrangement is that the slight up and down easing movement of thewhip roll is increased as the diameter of the warp beam is reduced, andif allowed to continue, becomesexcessive I am aware that mechanisms havebeen designed to deal with these difficulties, but my invention aims todevise a very simple and reliable means for automatically compensatingfor the change in let-oil required by a reduction in diameter of thebeam in such a manner as to maintain the position of the whip rollsubstantially unchanged throughout the weaving operation, holding thewarp continuously under practically a constant tension, and maintainingan approxi' mately uniform range of easing movement of the roll. 7

Referring again to Fig. l, I have attached a feeler 35 on a shaft 36where its upper end bears against the body of a yarn on beam 5. On theshaft 3%, outside the loom frame, is a finger 35a keyed, or set-screwed,to the shaft and connected to the spring 31 through the link 38. Thusthe spring holds the end of the feeler constantly against the peripheralsurface of the yarn body. An arm 4!) fast on the rock shaft M is joinedto the link 38 through a stud in a slot in the upper end of the arm.Also secured on the rock shaft 4! is an arm 42, the outer end of whichis forked and slotted to straddle a U-shaped wedge or tapered member 43,better shown in Figs. 2, 3 and 4. The arm 42 is. not connected directlyto the wedge 43, but its two parts are pivoted at is, respectively, tothe lower ends of two upright links 4545 and the upper end of the wedgeis pivoted to them, as shown at 56. It will be clear from an inspectionof the drawings that the wedge 63 is suspended from the upper ends ofthe two links 45 45; that it straddles the pawl operating rod 23; andalso that it is interposed between the adjacent ends of the driver 26and block 33.

When the beam is full, the connections between the feeler 35 and thewedge hold the latter with its relatively thin upper edge between theparts 28 and 23 where it is struck by the driver as the latter movestoward the right, Fig. 1, in producing the pawl actuating movement. Asthe yarn is unwound from the beam and its; diameter consequently isreduced, the wedge 33 is gradually raised. Consequently, it slowly fillsmore and more of the space between the driver 28 and the block 33 andthus gradually reduces the lost moion fraction of the fixed stroke ofthe driver 20 and increases its useful fraction. By properly designingthis member i3, the rate of increase of the let-01f movement of the pawlcan be made to bear the correct relationship to the gradual reduction indiameter of the beam so as to increase the rotative movement of the beamby the amount necessary to give the same let-off of warp at eachbeat-up, notwithstanding such changes in diameter.

The normal control over the idle position of the pawl Z5afiorded by thewhip roll 5 its connections with the rod 23 are not disturbed by the newarrangement, but both cooperate in exerting a joint control over thelength of stroke imparted to the pawl by the driver at each beatup. Inother words, the length of the stroke of the driver is fixed, but due toits lost motion connection with the pawl the fraction of its movementtoward the right, Fig. 1, up to the point at which it strikes the wedgeand moves it against the block 33 is idle. The remaining fraction of theright-hand stroke, however, is useful in operating the pawl. This usefulfraction therefore varies with the position of the wedge and suchposition, in turn, is controlled by the feeler bearing on the beam.Jointly with this control is that exerted by the position of the Whiproll since, if the roll moves either or down out of its normal position,it produces a corresponding change in position of the block and thusincreases or decreases the length of the stroke imparted to the pawl bythe driver.

With this arrangement, therefore, the whip roll remains continuously insubstantially the same position except, of course, for its slight easingmotion. The latter motion is of a constant amplitude and the tension onthe warp is not changed materially by the reduction in the diameter ofthe beam.

While I have herein shown and described a typical embodiment of myinvention, it will be understood that the invention may be embodied inother forms without departing from the spirit or scope thereof.

Having thus described my invention, what I desire to claim as new is:

1. In a loom provided with weaving instrumentalities including a warpbeam and a spring tensioned whiproll over which the warp yarns drawnfrom said beam are guided, the combination of mechanism for operatingthe beam to let off the warp as the weaving operation progresses, meansgoverned by the position of said roll for controlling the let-01foperation, a feeler yieldingly held in contact with the yarn body onsaid beam, and a tapered member controlled as to position by said feelerand cooperating with said means in controlling said let-off operation.

2. In a loom provided with weaving instrumentalities including a warpbeam and a spring tensioned whip roll over which the warp yarns drawnfrom said beam are guided, the combination of mechanism for operatingthe beam to let off the warp as the weaving operation progresses; saidmechanism including a pawl, a ratchet wheel operated thereby, and areciprocating driver for said pawl having a lost motion connectiontherewith; a feeler yieldingly held in contact with the yarn body on thebeam, and means operated by said feeler and cooperating with said whiproll to determine the fraction of the stroke of said driver that will beutilized in operating said pawl during successive reciprocations of thedriver.

3. In a loom provided with weaving instrumentalities including a warpbeam and a spring tensioned whip roll over which the warp yarns drawnfrom said beam are guided, the ccn1bination of mechanism for operatingthe beam to let off the warp as the weaving operation progresses; saidmechanism including a pawl, a ratchet wheel operated thereby, and areciprocating driver for said pawl having a lost motion connectiontherewith; a feeler yieldingly held in contact with the yarn body on thebeam, and a tapered member so connected with said ieeler that itsposition is controlled thereby, saidmember being so associated with saiddriver as to gradually increase the fraction of the stroke of saiddriver utilized in operating said let-off mechanism as the diameter ofsaid yarn body is reduced.

4. In a loom provided with Weaving instrumentalities including a Warpbeam and a spring tensioned whip roll over which the warp yarns drawnfrom said beam are guided, thecombination of mechanism for operating thebeam to let off the warp as the weaving operation progresses; saidmechanism including a pawl, a ratchet wheel operated thereby, and areciprocating driver for said pawl having an operating stroke of fixedlength and a lost motion connection with the pawl; means adjustablerelatively to said driver for controlling the degree of its lost motion,a feeler yieldingly held in contact with the yarn body on said beam, andconnections between said feeler and said means for adjusting the latterand thereby-changing the degree of said lost motion, in accordancewithchanges in the diameter of the yarn body.

5. In a loom provided with weavmg instrumentalities including a warpbeam and a spring tensioned whip roll over which the warp yarns drawnfrom said beam are guided, the combination of mechanism for operatingthe beam to let 01f the warp as the weaving operation progresses; saidmechanism including a pawl, a ratchet wheel operated thereby, areciprocating driver for said pawl, and a rod connecting said pawl withsaid driver and having a lost motion relationship to the latter; a wedgestraddling said rod and interposed between said driver and a fixedmember on it, a feeler yieldingly held in contact with the yarn body onthe beam, and connections between said feeler and said wedge for adjusting the latter transversely of the rod and thereby changing the fractionof thestroke of said driver utilized in operating said pawl as said yarnbody changes in diameter.

6. In a loom organization according to preceding claim 5, in combinationwith means connecting said rod with said whip roll and serving to shiftthe position of the rod axially with reference toboth the driver andsaid wedge in accordance with changes in the position of the whip roll,whereby the let-01f action produced by the movement of the driver iscontrolled jointly by the position of said whip roll and the diam,- eterof said "yam body.

IVAR O. MOBERG.

